A lubricant dispenser of the aforedescribed type can comprise a housing or receptacle for a flowable lubricant, e.g. oil or grease, which has a fitting enabling connection of the receptacle to a part of the machine and provided with a lubricant passage through which the lubricant is delivered to the machine.
On the opposite side of the receptacle, a pressurizing source is provided and between the pressurizing source and lubricant, a piston is located for forcing the lubricant progressively out of the receptacle and, more particularly, displacing the lubricant from the passage at a certain rate or quantity of lubricant per unit time. The source of pressure can be a gas generator and when the latter is set in operation, causes slow, long-term and continuous release of the lubricant terminating with the end of gas generation. It will be understood, of course, that the generation of gas can also be interrupted in the course of lubrication as may be required.
In one known system for dispensing lubricant (see German patent document DE 38 11 469 A1 and U.S. Pat. No. 5,012,897), the housing is closed on its side opposite the connecting fitting by a bottom formed on the receptacle. This bottom has a central recess or cutout. The connecting fitting is formed in a cover engaging the wall of the receptacle or housing and held thereon by a fold seam. The gas-generating means does not form an independent unit and comprises a bottom part and an elastic hood which is connected with the bottom part.
In the bottom part of the gas generator a cartridge seat is provided, this seat being closed off from the elastic hood by a partition. The space between the source and the hood is filled with a gas-generating liquid and hood and its associated parts are mounted prior to insertion of the cover in the housing. The piston is then inserted into the housing and the cover with its connecting fitting is applied.
The piston is not directly pressurized by the gas but rather is pressed against the lubricant by the expanding elastic hood, the latter being inflated by the development of gas from the liquid.
In the central recess of the bottom, a cartridge is introduced and can be screwed into the seat, the partition rupturing or being otherwise destroyed. The cartridge itself has a space for the gas-generating elements and closed by a membrane-like wall which is galvanically destroyed when the cartridge is screwed into place and the gas-generating liquid comes into contact with this partition wall.
In practice this construction of a lubricant dispenser has been found to be expensive to fabricate and excessively complex. It can be improved operationally as well since the gas pressure is partly dissipated in this system by the need to expand the hood via elastic deformation.
In German patent document DE 37 18 341 C2, another type of lubricant dispenser is provided in which the gas generator is also not a self-contained or independent unit. Here the gas generator is a space within the receptacle or housing separated by the piston from the lubricant supply. The separated space serves to hold the generated gas and the gas generation is effected with the aid of a special gas-generating element which is disposed in the piston. The gas-generating element can be a electrolyte vessel in which a corrosion element which passes into solution with the generation of gas, is in contact with the electrolyte. Another type of gas-generating element which may be used in this case is an electrolyte vessel in which an anode and cathode are immersed in the electrolyte and which generates gas when an electric current is passed through the cell formed by the anode and cathode. For this purpose an appropriate electric circuit is provided.
In this embodiment as well, the connecting fitting is provided on a cover which is connected with the housing or receptacle wall by a fold seam. The cover is applied once the piston with its gas-generating element has been introduced into the housing or receptacle. From the bottom of the housing the electrical conductor extends outwardly. As a practical matter, this lubricant dispenser has not found widespread application.
Yet another lubricant dispenser is described in WO 89/08800 in which the gas generation produces a piston displacement and forces lubricant out of the receptacle in the manner described. The electrochemistry of the system, however, is somewhat different (see DE 35 32 335 C2). This system operates with so-called battery cells. Here the gas development can be induced or interrupted via the cutting in or cutting out of the battery in a simple manner. By the additional provision of an adjustable potentiometer, the gas generation and the lubricant flow rate can be controlled.
Finally, reference may be had to German patent DE 42 09 776.2 A1 and the aforementioned copending application which describes a gas-generating unit as a self-contained unit and which is comprised of a bottom part, a cartridge seat and a cover cap and which can be inserted into a recess of the housing to form a bottom thereof which can be removably anchored in the housing. The cover cap is so connected to the bottom part that it can be shoved off the latter upon the development of gas pressure in the cartridge or by the cartridge. The cover cap here functions as the lubricant displacing piston.
The device is so constructed that in the virgin state, the gas-generating cell is disposed in the space between the bottom part and the cover cap and includes a gas-generating liquid which comes into contact with an element producing the gas, this element being separated in the virgin state by a partition from the liquid. The partition is ruptured or destroyed by the actuation of a mechanical device for switching on the feed of lubricant from the receptacle so that the gas-generating element can come into contact with the gas-generating liquid and produce gas. The gas pressure which is thus produced drives the piston off the bottom and enables its displacement to force lubricant out of the container. This system has been found to be satisfactory but also requires improvement since the handling of a liquid-filled element and its fabrication is inconvenient.